This theory is often floated but nothing I see supports it

We discussed in Rocco linked to Michael thread, killing Roth need not have been a suicide one-way mission
He was like a deer caught in headlights, having no escape plans whatsoever

Neri already had Fredo's job so Rocco got Roth's job

Tom's demotion was because as Vito himself put it, there are reasons why he must have no part in what is going to happen.

Tom "my lawyer," and Rocco didn't sit in on the Cuba negotiations with Ola.
Neri as Michael's bodyguard is always with him, bodyguarding him

True The Master Manipulator knew exactly which buttons to push, for brother Tom
I will have to watch again but as I remember, there were no orders from Tom to Neri

Michael shouted in anger at Tom as soon as he got back because he couldn't give him a straight answer anymore!
Sonny had lashed out at Tom too

Tom asked the question in front of Rocco and Neri. Why did you ask me if something was wrong when I came in?
So Michael answered in front of Rocco and Neri.

he's in Israel Then trying to discourage killing Roth who will always be a threat to Michael. Duh!